diff --git a/js/src/ctypes/CTypes.cpp b/js/src/ctypes/CTypes.cpp
index 038602d98075..d1c714dee196 100644
--- a/js/src/ctypes/CTypes.cpp
+++ b/js/src/ctypes/CTypes.cpp
@@ -2273,6 +2273,7 @@ InitTypeClasses(JSContext* cx, HandleObject ctypesObj)
   // Attach objects representing ABI constants.
   if (!DefineABIConstant(cx, ctypesObj, "default_abi", ABI_DEFAULT, ABIProto) ||
       !DefineABIConstant(cx, ctypesObj, "stdcall_abi", ABI_STDCALL, ABIProto) ||
+      !DefineABIConstant(cx, ctypesObj, "thiscall_abi", ABI_THISCALL, ABIProto) ||
       !DefineABIConstant(cx, ctypesObj, "winapi_abi", ABI_WINAPI, ABIProto))
     return false;
 
@@ -3917,6 +3918,8 @@ BuildTypeName(JSContext* cx, JSObject* typeObj_)
       ABICode abi = GetABICode(fninfo->mABI);
       if (abi == ABI_STDCALL)
         PrependString(result, "__stdcall");
+      else if (abi == ABI_THISCALL)
+        PrependString(result, "__thiscall");
       else if (abi == ABI_WINAPI)
         PrependString(result, "WINAPI");
 
@@ -4022,6 +4025,9 @@ BuildTypeSource(JSContext* cx,
     case ABI_STDCALL:
       AppendString(result, "ctypes.stdcall_abi, ");
       break;
+    case ABI_THISCALL:
+      AppendString(result, "ctypes.thiscall_abi, ");
+      break;
     case ABI_WINAPI:
       AppendString(result, "ctypes.winapi_abi, ");
       break;
@@ -5012,6 +5018,9 @@ ABI::ToSource(JSContext* cx, unsigned argc, Value* vp)
     case ABI_STDCALL:
       result = JS_NewStringCopyZ(cx, "ctypes.stdcall_abi");
       break;
+    case ABI_THISCALL:
+      result = JS_NewStringCopyZ(cx, "ctypes.thiscall_abi");
+      break;
     case ABI_WINAPI:
       result = JS_NewStringCopyZ(cx, "ctypes.winapi_abi");
       break;
@@ -6547,6 +6556,16 @@ GetABI(JSContext* cx, Value abiType, ffi_abi* result)
   case ABI_DEFAULT:
     *result = FFI_DEFAULT_ABI;
     return true;
+  case ABI_THISCALL:
+#if defined(_WIN64)
+    *result = FFI_WIN64;
+    return true;
+#elif defined(_WIN32)
+    *result = FFI_THISCALL;
+    return true;
+#else
+    break;
+#endif
   case ABI_STDCALL:
   case ABI_WINAPI:
 #if (defined(_WIN32) && !defined(_WIN64)) || defined(_OS2)
@@ -6692,6 +6711,7 @@ FunctionType::BuildSymbolName(JSString* name,
 
   switch (GetABICode(fninfo->mABI)) {
   case ABI_DEFAULT:
+  case ABI_THISCALL:
   case ABI_WINAPI:
     // For cdecl or WINAPI functions, no mangling is necessary.
     AppendString(result, name);
diff --git a/js/src/ctypes/CTypes.h b/js/src/ctypes/CTypes.h
index 6e44fa6f0382..7289dcba0b17 100644
--- a/js/src/ctypes/CTypes.h
+++ b/js/src/ctypes/CTypes.h
@@ -211,6 +211,7 @@ enum ErrorNum {
 enum ABICode {
   ABI_DEFAULT,
   ABI_STDCALL,
+  ABI_THISCALL,
   ABI_WINAPI,
   INVALID_ABI
 };
diff --git a/toolkit/components/ctypes/tests/jsctypes-test.cpp b/toolkit/components/ctypes/tests/jsctypes-test.cpp
index 0d5a5282f10b..91eee2420b79 100644
--- a/toolkit/components/ctypes/tests/jsctypes-test.cpp
+++ b/toolkit/components/ctypes/tests/jsctypes-test.cpp
@@ -384,3 +384,15 @@ test_vector_add_va_cdecl(uint8_t num_vecs,
 }
 
 myRECT data_rect = { -1, -2, 3, 4 };
+
+TestClass::TestClass(int32_t a)
+{
+  mInt =a;
+}
+
+int32_t
+TestClass::Add(int32_t aOther)
+{
+  mInt += aOther;
+  return mInt;
+}
diff --git a/toolkit/components/ctypes/tests/jsctypes-test.h b/toolkit/components/ctypes/tests/jsctypes-test.h
index 5fec2238ef45..14eb8c9152d4 100644
--- a/toolkit/components/ctypes/tests/jsctypes-test.h
+++ b/toolkit/components/ctypes/tests/jsctypes-test.h
@@ -185,4 +185,13 @@ MOZ_BEGIN_EXTERN_C
 
 MOZ_END_EXTERN_C
 
+class MOZ_EXPORT TestClass final {
+public:
+  explicit TestClass(int32_t);
+  int32_t Add(int32_t);
+
+private:
+  int32_t mInt;
+};
+
 #endif
diff --git a/toolkit/components/ctypes/tests/unit/test_jsctypes.js b/toolkit/components/ctypes/tests/unit/test_jsctypes.js
index 0a564dfa9221..57d54a8eebef 100644
--- a/toolkit/components/ctypes/tests/unit/test_jsctypes.js
+++ b/toolkit/components/ctypes/tests/unit/test_jsctypes.js
@@ -182,6 +182,7 @@ function run_test()
   run_closure_tests(library);
   run_variadic_tests(library);
   run_static_data_tests(library);
+  run_cpp_class_tests(library);
 
   // test library.close
   let test_void_t = library.declare("test_void_t_cdecl", ctypes.default_abi, ctypes.void_t);
@@ -2791,6 +2792,42 @@ function run_static_data_tests(library)
   do_check_eq(ptrValue(data_rect.address()), ptrValue(data_rect_2.address()));
 }
 
+function run_cpp_class_tests(library)
+{
+  // try the gcc mangling, unless we're using MSVC.
+  let OS = get_os();
+  let ctor_symbol;
+  let add_symbol;
+  let abi;
+  if (OS == "WINNT") {
+    // for compatibility for Win32 vs Win64
+    abi = ctypes.thiscall_abi;
+    if (ctypes.size_t.size == 8) {
+      ctor_symbol = '??0TestClass@@QEAA@H@Z';
+      add_symbol = '?Add@TestClass@@QEAAHH@Z';
+    } else {
+      ctor_symbol = '??0TestClass@@QAE@H@Z';
+      add_symbol = '?Add@TestClass@@QAEHH@Z';
+    }
+  } else {
+    abi = ctypes.default_abi;
+    ctor_symbol = "_ZN9TestClassC1Ei";
+    add_symbol = "_ZN9TestClass3AddEi";
+  }
+
+  let test_class_ctor = library.declare(ctor_symbol, abi, ctypes.void_t,
+                                        ctypes.int32_t.ptr, ctypes.int32_t);
+  let i = ctypes.int32_t();
+  test_class_ctor(i.address(), 8);
+  do_check_eq(i.value, 8);
+
+  let test_class_add = library.declare(add_symbol, abi, ctypes.int32_t,
+                                       ctypes.int32_t.ptr, ctypes.int32_t);
+  let j = test_class_add(i.address(), 5);
+  do_check_eq(j, 13);
+  do_check_eq(i.value, 13);
+}
+
 // bug 522360 - try loading system library without full path
 function run_load_system_library()
 {